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4.6.4
Time base generator circuit
The drive uses constant density recording to increase total capacity. This is different from the
conventional method of recording data with a fixed data transfer rate at all data area. In the
constant density recording method, data area is divided into zones by radius and the data
transfer rate is set so that the recording density of the inner cylinder of each zone is nearly
constant. The drive divides data area into 15 zones to set the data transfer rate. Table 4.2
describes the data transfer rate and recording density (BPI) of each zone.
Table 4.2
Zone
0
Cylinder
0
to
1308
Transfer rate
34.67
[MB/s]
Zone
8
Cylinder
8249
to
8638
Transfer rate
28.63
[MB/s]
The MPU transfers the data transfer rate setup data (SDATA/SCLK) to the RDC that includes
the time base generator circuit to change the data transfer rate.
4.7
Servo Control
The actuator motor and the spindle motor are submitted to servo control. The actuator motor
is controlled for moving and positioning the head to the track containing the desired data. To
turn the disk at a constant velocity, the actuator motor is controlled according to the servo data
that is written on the data side beforehand.
Write clock frequency and transfer rate of each zone
1
2
3
1309
2617
3915
to
to
to
2616
3914
4868
34.67
34.67
33.57
9
10
11
8639
9419
10009
to
to
to
9418
10008
10598
27.53
26.62
25.70
C141-E072-01EN
4
5
6
4869
5649
6329
to
to
to
5648
6328
7468
32.66
31.76
30.25
12
13
14
10599
11526
12163
to
to
to
11525
12162
12554
24.20
23.14
21.47
7
7469
to
8248
29.18
4 - 13
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